The point is not to recreate it or explain it, or to have a way to say "tweet X will get rank Y" but to open source what there is. It doesn't matter if no single person can explain it, it'll still be open source and readable and the types of inputs will be known. But this doesn't look like a discussion on open source and more about politics at this point.

I for one haven't worked at FAANG and think it'll be super interesting to read this code, I can't believe software engineers are complaining about a potentially super complex bleeding edge codebase for timeline recommendations / ranking being open sourced. This is going to be great reading material if it ever gets published!

Nobody is trying to “recreate a perfect copy” of Twitter. Do you think that code which produces random numbers is also not an algorithm because it doesn’t recreate a perfect copy of a previous random number?

No you can't, you can only make a twin, but the mind is shaped by experience also and not just genetics. As is the body.

Is there any reason to not think that like most human-created systems it has a mixture of intentional and unintentional bias?

In that case, the algorithm is the labels.